A computed tomography (CT) scanner includes a rotating portion rotatably supported by a stationary portion. The rotating portion supports an x-ray tube, which emits radiation that traverses an examination region, and a detector array that detects radiation traversing the examination region. A conventional integrating detector array includes a scintillator array optically coupled to a photodiode array. The scintillator array absorbs x-ray photons and emits light photons indicative thereof, and the photodiode array receives the light photons and generates electrical signals indicative thereof and hence the absorbed x-ray photons. A reconstructor reconstructs the signals and generates volumetric image data indicative of the examination.
Various approaches have been used to couple the scintillator and detector arrays. One approach is discussed in connection with FIGS. 1A and 1B. FIG. 1A shows a two dimensional photodiode array 102. Generally, such arrays are 16×16 up to 16×64; however, for explanatory purposes, the illustrated array is a 2×2 array with four generally square shaped detector elements 104. Each detector element 104 includes a surface 106 with a light sensitive region 108 surrounded by a non-sensitive region 110. A drop of an optical adhesive 112 is placed at a junction 114 where the four detector pixels 104 meet. A scintillator array 116 is then lowered onto the photodiode array 102. As the scintillator array 116 physically contacts the optical adhesive 112 and applies a force thereon, the optical adhesive 112 radially spreads from the junction 114 over the surface 106, including both the light sensitive regions 108 and the non-sensitive regions 110. FIG. 1B shows the scintillator array 116 lowered onto the photodiode array 102 with the optical adhesive 112 there between.
With this approach, as well as other approaches, optical adhesive voids (or air bubbles) may form and be trapped between the scintillator array 116 and the photodiode array 102. Unfortunately, such voids may decrease light collection efficiency, i.e., inhibit or prevent light transmission from the scintillator array 116 to the light sensitive regions 108 of the photodiode pixels 104. Furthermore, it can be difficult to control the final optical adhesive thickness between the scintillator array 116 and the photodiode array 102, and excess adhesive 118 will squeeze out of the sides, as shown in FIG. 1B, and must be subsequently removed. Moreover, this approach requires fixtures to hold the scintillator array 116 and the photodiode array 102 in place, and the automation machinery generally is expensive.